Seven Possible Reasons Your Precision Parts are Out of Tolerance (Part 2)
There’s a reason these parts are called “close tolerance” or “precision” parts. There is little, if any, room for error. So, when a part is out of tolerance, it needs to be addressed immediately; otherwise, you and/or your customer are in for a lot of trouble.
In Part 1, we covered three possible reasons your parts are out of tolerance:
Material Shrinkage Rages
The Injection Mold Process
Imbalanced Gates/Hot Runner Systems
Today, we’re going to cover four more things that might be causing your precision parts to be out of tolerance.
4. Improper Venting - during the molding process, air inside the cavity needs to be evacuated for the plastic to fill the cavity. If proper venting isn’t present, this causes inadequate filling, resulting in several potential defects.
Vent Isn’t Deep Enough - vent depth is critical. It needs to allow for the evacuation of air but not let the plastic escape.
Not Enough Venting - all molds require both a primary vent and a vent dump to atmosphere to prevent burns, voids and steel corrosion.
No Venting - sometimes venting simply is ignored or not fully considered in the design and build process.
5. Worn or Corroded Steel Components - over time, especially if a proper maintenance schedule isn’t in place, the steel parts in a mold can become worn or corroded.
Regularly Scheduled Maintenance - this issue of worn or corroded steel components can be almost 100 percent avoided if a regular maintenance schedule is implemented.
Replaced - if corrosion exists it might be beyond repair and require a full replacement of that component to get your part back in tolerance.
Welded and Remachined - sometimes a “bad” component can be welded or remachined, rather than needing a full replacement.
6. Insufficient Cooling - temperature plays a vital role in part quality when it comes to plastic injection molding; otherwise you can face such defects as warping, jetting, sink marks and more.
Bad Design - at its simplest level, poor cooling in the injection molding process is the result of poor design of the mold.
Improper Plumbing - because temperature is such a vital component in the plastic injection molding process, even something as simple as issues with your plumbing could create issues in the cooling system.
Auxiliary Equipment Issues - using a thermolator or chiller can help achieve the proper water supply temperature. If these are not performing effectively/efficiently, this could lead to defects in the end product.
7. Inconsistent Wall Thickness - wall thickness can have a significant impact on the cost, production speed, and final quality of a part.
Bad part design - inconsistent wall thickness is a direct result of the engineering and design of a mold/tool. If this is an issue, unfortunately, the most likely solution is a new mold that’s redesigned with wall thickness in mind, while also addressing all the other areas we have discussed in these two posts.
If you are struggling to maintain consistency in the production of your close tolerance parts, it could be related to one of the issues above. We would love to talk through these possible problems with you and see if there’s some way we can help.
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